diff --git a/core/mem/mem.odin b/core/mem/mem.odin
index a56702ae8..fe2be4cf6 100644
--- a/core/mem/mem.odin
+++ b/core/mem/mem.odin
@@ -2,7 +2,7 @@ package mem
 
 import "core:runtime"
 
-set :: proc "contextless" (data: rawptr, value: byte, len: int) -> rawptr {
+set :: proc(data: rawptr, value: byte, len: int) -> rawptr {
 	foreign _ {
 		when ODIN_USE_LLVM_API {
 			when size_of(rawptr) == 8 {
@@ -26,26 +26,26 @@ set :: proc "contextless" (data: rawptr, value: byte, len: int) -> rawptr {
 	memset(data, value, len);
 	return data;
 }
-zero :: inline proc "contextless" (data: rawptr, len: int) -> rawptr {
+zero :: inline proc(data: rawptr, len: int) -> rawptr {
 	return set(data, 0, len);
 }
-zero_item :: inline proc "contextless" (item: $P/^$T) {
+zero_item :: inline proc(item: $P/^$T) {
 	set(item, 0, size_of(T));
 }
-zero_slice :: proc "contextless" (data: $T/[]$E) {
+zero_slice :: proc(data: $T/[]$E) {
 	if n := len(data); n > 0 {
 		zero(&data[0], size_of(E)*n);
 	}
 }
 
 
-copy :: proc "contextless" (dst, src: rawptr, len: int) -> rawptr {
+copy :: proc(dst, src: rawptr, len: int) -> rawptr {
 	return runtime.mem_copy(dst, src, len);
 }
-copy_non_overlapping :: proc "contextless" (dst, src: rawptr, len: int) -> rawptr {
+copy_non_overlapping :: proc(dst, src: rawptr, len: int) -> rawptr {
 	return runtime.mem_copy_non_overlapping(dst, src, len);
 }
-compare :: inline proc "contextless" (a, b: []byte) -> int {
+compare :: inline proc(a, b: []byte) -> int {
 	// NOTE(tetra): no-abc is okay here because if the slices are empty, `&a[0]` is just nil+0 == nil, which
 	// compare_byte_ptrs handles fine when the passed length is also zero.
 	res := #no_bounds_check compare_byte_ptrs(&a[0], &b[0], min(len(a), len(b)));
@@ -57,7 +57,7 @@ compare :: inline proc "contextless" (a, b: []byte) -> int {
 	return res;
 }
 
-compare_byte_ptrs :: proc "contextless" (a, b: ^byte, n: int) -> int #no_bounds_check {
+compare_byte_ptrs :: proc(a, b: ^byte, n: int) -> int #no_bounds_check {
 	x := slice_ptr(a, n);
 	y := slice_ptr(b, n);
 
@@ -91,36 +91,36 @@ compare_byte_ptrs :: proc "contextless" (a, b: ^byte, n: int) -> int #no_bounds_
 	return 0;
 }
 
-compare_ptrs :: inline proc "contextless" (a, b: rawptr, n: int) -> int {
+compare_ptrs :: inline proc(a, b: rawptr, n: int) -> int {
 	return compare_byte_ptrs((^byte)(a), (^byte)(b), n);
 }
 
-ptr_offset :: inline proc "contextless" (ptr: $P/^$T, n: int) -> P {
+ptr_offset :: inline proc(ptr: $P/^$T, n: int) -> P {
 	new := int(uintptr(ptr)) + size_of(T)*n;
 	return P(uintptr(new));
 }
 
-ptr_sub :: inline proc "contextless" (a, b: $P/^$T) -> int {
+ptr_sub :: inline proc(a, b: $P/^$T) -> int {
 	return (int(uintptr(a)) - int(uintptr(b)))/size_of(T);
 }
 
-slice_ptr :: inline proc "contextless" (ptr: ^$T, len: int) -> []T {
+slice_ptr :: inline proc(ptr: ^$T, len: int) -> []T {
 	assert(len >= 0);
 	return transmute([]T)Raw_Slice{data = ptr, len = len};
 }
 
-slice_ptr_to_bytes :: proc "contextless" (ptr: rawptr, len: int) -> []byte {
+slice_ptr_to_bytes :: proc(ptr: rawptr, len: int) -> []byte {
 	assert(len >= 0);
 	return transmute([]byte)Raw_Slice{data = ptr, len = len};
 }
 
-slice_to_bytes :: inline proc "contextless" (slice: $E/[]$T) -> []byte {
+slice_to_bytes :: inline proc(slice: $E/[]$T) -> []byte {
 	s := transmute(Raw_Slice)slice;
 	s.len *= size_of(T);
 	return transmute([]byte)s;
 }
 
-slice_data_cast :: inline proc "contextless" ($T: typeid/[]$A, slice: $S/[]$B) -> T {
+slice_data_cast :: inline proc($T: typeid/[]$A, slice: $S/[]$B) -> T {
 	when size_of(A) == 0 || size_of(B) == 0 {
 		return nil;
 	} else {
@@ -130,7 +130,7 @@ slice_data_cast :: inline proc "contextless" ($T: typeid/[]$A, slice: $S/[]$B) -
 	}
 }
 
-slice_to_components :: proc "contextless" (slice: $E/[]$T) -> (data: ^T, len: int) {
+slice_to_components :: proc(slice: $E/[]$T) -> (data: ^T, len: int) {
 	s := transmute(Raw_Slice)slice;
 	return s.data, s.len;
 }
@@ -145,22 +145,22 @@ buffer_from_slice :: inline proc(backing: $T/[]$E) -> [dynamic]E {
 	};
 }
 
-ptr_to_bytes :: inline proc "contextless" (ptr: ^$T, len := 1) -> []byte {
+ptr_to_bytes :: inline proc(ptr: ^$T, len := 1) -> []byte {
 	assert(len >= 0);
 	return transmute([]byte)Raw_Slice{ptr, len*size_of(T)};
 }
 
-any_to_bytes :: inline proc "contextless" (val: any) -> []byte {
+any_to_bytes :: inline proc(val: any) -> []byte {
 	ti := type_info_of(val.id);
 	size := ti != nil ? ti.size : 0;
 	return transmute([]byte)Raw_Slice{val.data, size};
 }
 
 
-kilobytes :: inline proc "contextless" (x: int) -> int do return          (x) * 1024;
-megabytes :: inline proc "contextless" (x: int) -> int do return kilobytes(x) * 1024;
-gigabytes :: inline proc "contextless" (x: int) -> int do return megabytes(x) * 1024;
-terabytes :: inline proc "contextless" (x: int) -> int do return gigabytes(x) * 1024;
+kilobytes :: inline proc(x: int) -> int do return          (x) * 1024;
+megabytes :: inline proc(x: int) -> int do return kilobytes(x) * 1024;
+gigabytes :: inline proc(x: int) -> int do return megabytes(x) * 1024;
+terabytes :: inline proc(x: int) -> int do return gigabytes(x) * 1024;
 
 is_power_of_two :: inline proc(x: uintptr) -> bool {
 	if x <= 0 do return false;
diff --git a/core/runtime/core.odin b/core/runtime/core.odin
index c1ecc4b9c..a40e6d005 100644
--- a/core/runtime/core.odin
+++ b/core/runtime/core.odin
@@ -518,7 +518,7 @@ copy :: proc{copy_slice, copy_from_string};
 
 
 @builtin
-pop :: proc "contextless" (array: ^$T/[dynamic]$E) -> E {
+pop :: proc(array: ^$T/[dynamic]$E) -> E {
 	if array == nil do return E{};
 	assert(len(array) > 0);
 	res := #no_bounds_check array[len(array)-1];
@@ -1270,7 +1270,7 @@ __get_map_key :: proc "contextless" (k: $K) -> Map_Key {
 	return map_key;
 }
 
-_fnv64a :: proc(data: []byte, seed: u64 = 0xcbf29ce484222325) -> u64 {
+_fnv64a :: proc "contextless" (data: []byte, seed: u64 = 0xcbf29ce484222325) -> u64 {
 	h: u64 = seed;
 	for b in data {
 		h = (h ~ u64(b)) * 0x100000001b3;
@@ -1279,10 +1279,10 @@ _fnv64a :: proc(data: []byte, seed: u64 = 0xcbf29ce484222325) -> u64 {
 }
 
 
-default_hash :: proc(data: []byte) -> u64 {
+default_hash :: proc "contextless" (data: []byte) -> u64 {
 	return _fnv64a(data);
 }
-default_hash_string :: proc(s: string) -> u64 do return default_hash(transmute([]byte)(s));
+default_hash_string :: proc "contextless" (s: string) -> u64 do return default_hash(transmute([]byte)(s));
 
 
 source_code_location_hash :: proc(s: Source_Code_Location) -> u64 {
diff --git a/core/runtime/internal.odin b/core/runtime/internal.odin
index 9788c0633..a89c0580d 100644
--- a/core/runtime/internal.odin
+++ b/core/runtime/internal.odin
@@ -583,6 +583,7 @@ quaternion256_ne :: inline proc "contextless" (a, b: quaternion256) -> bool { re
 bounds_check_error :: proc "contextless" (file: string, line, column: int, index, count: int) {
 	if 0 <= index && index < count do return;
 	handle_error :: proc "contextless" (file: string, line, column: int, index, count: int) {
+		context = default_context();
 		fd := os.stderr;
 		print_caller_location(fd, Source_Code_Location{file, line, column, "", 0});
 		os.write_string(fd, " Index ");
@@ -596,6 +597,7 @@ bounds_check_error :: proc "contextless" (file: string, line, column: int, index
 }
 
 slice_handle_error :: proc "contextless" (file: string, line, column: int, lo, hi: int, len: int) {
+	context = default_context();
 	fd := os.stderr;
 	print_caller_location(fd, Source_Code_Location{file, line, column, "", 0});
 	os.write_string(fd, " Invalid slice indices: ");
@@ -621,6 +623,7 @@ slice_expr_error_lo_hi :: proc "contextless" (file: string, line, column: int, l
 dynamic_array_expr_error :: proc "contextless" (file: string, line, column: int, low, high, max: int) {
 	if 0 <= low && low <= high && high <= max do return;
 	handle_error :: proc "contextless" (file: string, line, column: int, low, high, max: int) {
+		context = default_context();
 		fd := os.stderr;
 		print_caller_location(fd, Source_Code_Location{file, line, column, "", 0});
 		os.write_string(fd, " Invalid dynamic array values: ");
@@ -639,6 +642,7 @@ dynamic_array_expr_error :: proc "contextless" (file: string, line, column: int,
 type_assertion_check :: proc "contextless" (ok: bool, file: string, line, column: int, from, to: typeid) {
 	if ok do return;
 	handle_error :: proc "contextless" (file: string, line, column: int, from, to: typeid) {
+		context = default_context();
 		fd := os.stderr;
 		print_caller_location(fd, Source_Code_Location{file, line, column, "", 0});
 		os.write_string(fd, " Invalid type assertion from ");
@@ -751,6 +755,7 @@ dynamic_array_expr_error_loc :: inline proc "contextless" (using loc := #caller_
 make_slice_error_loc :: inline proc "contextless" (loc := #caller_location, len: int) {
 	if 0 <= len do return;
 	handle_error :: proc "contextless" (loc: Source_Code_Location, len: int) {
+		context = default_context();
 		fd := os.stderr;
 		print_caller_location(fd, loc);
 		os.write_string(fd, " Invalid slice length for make: ");
@@ -764,6 +769,7 @@ make_slice_error_loc :: inline proc "contextless" (loc := #caller_location, len:
 make_dynamic_array_error_loc :: inline proc "contextless" (using loc := #caller_location, len, cap: int) {
 	if 0 <= len && len <= cap do return;
 	handle_error :: proc "contextless" (loc: Source_Code_Location, len, cap: int) {
+		context = default_context();
 		fd := os.stderr;
 		print_caller_location(fd, loc);
 		os.write_string(fd, " Invalid dynamic array parameters for make: ");
@@ -779,6 +785,7 @@ make_dynamic_array_error_loc :: inline proc "contextless" (using loc := #caller_
 make_map_expr_error_loc :: inline proc "contextless" (loc := #caller_location, cap: int) {
 	if 0 <= cap do return;
 	handle_error :: proc "contextless" (loc: Source_Code_Location, cap: int) {
+		context = default_context();
 		fd := os.stderr;
 		print_caller_location(fd, loc);
 		os.write_string(fd, " Invalid map capacity for make: ");
diff --git a/core/sync/atomic.odin b/core/sync/atomic.odin
index 996c14f47..ba324e96d 100644
--- a/core/sync/atomic.odin
+++ b/core/sync/atomic.odin
@@ -10,7 +10,7 @@ Ordering :: enum {
 	Sequentially_Consistent,
 }
 
-strongest_failure_ordering :: inline proc "contextless" (order: Ordering) -> Ordering {
+strongest_failure_ordering :: inline proc(order: Ordering) -> Ordering {
 	switch order {
 	case .Relaxed:                 return .Relaxed;
 	case .Release:                 return .Relaxed;
@@ -21,7 +21,7 @@ strongest_failure_ordering :: inline proc "contextless" (order: Ordering) -> Ord
 	return .Relaxed;
 }
 
-fence :: inline proc "contextless" ($order: Ordering) {
+fence :: inline proc($order: Ordering) {
 	switch order {
 	case .Relaxed:                 panic("there is no such thing as a relaxed fence");
 	case .Release:                 intrinsics.atomic_fence_rel();
@@ -33,7 +33,7 @@ fence :: inline proc "contextless" ($order: Ordering) {
 }
 
 
-atomic_store :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) {
+atomic_store :: inline proc(dst: ^$T, val: T, $order: Ordering) {
 	switch order {
 	case .Relaxed:                 intrinsics.atomic_store_relaxed(dst, val);
 	case .Release:                 intrinsics.atomic_store_rel(dst, val);
@@ -44,7 +44,7 @@ atomic_store :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) {
 	}
 }
 
-atomic_load :: inline proc "contextless" (dst: ^$T, $order: Ordering) -> T {
+atomic_load :: inline proc(dst: ^$T, $order: Ordering) -> T {
 	switch order {
 	case .Relaxed:                 return intrinsics.atomic_load_relaxed(dst);
 	case .Acquire:                 return intrinsics.atomic_load_acq(dst);
@@ -56,7 +56,7 @@ atomic_load :: inline proc "contextless" (dst: ^$T, $order: Ordering) -> T {
 	return T{};
 }
 
-atomic_swap :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) -> T {
+atomic_swap :: inline proc(dst: ^$T, val: T, $order: Ordering) -> T {
 	switch order {
 	case .Relaxed:                 return intrinsics.atomic_xchg_relaxed(dst, val);
 	case .Release:                 return intrinsics.atomic_xchg_rel(dst, val);
@@ -68,7 +68,7 @@ atomic_swap :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) ->
 	return T{};
 }
 
-atomic_compare_exchange :: inline proc "contextless" (dst: ^$T, old, new: T, $success, $failure: Ordering) -> (val: T, ok: bool) {
+atomic_compare_exchange :: inline proc(dst: ^$T, old, new: T, $success, $failure: Ordering) -> (val: T, ok: bool) {
 	switch failure {
 	case .Relaxed:
 		switch success {
@@ -102,7 +102,7 @@ atomic_compare_exchange :: inline proc "contextless" (dst: ^$T, old, new: T, $su
 
 }
 
-atomic_compare_exchange_weak :: inline proc "contextless" (dst: ^$T, old, new: T, $success, $failure: Ordering) -> (val: T, ok: bool) {
+atomic_compare_exchange_weak :: inline proc(dst: ^$T, old, new: T, $success, $failure: Ordering) -> (val: T, ok: bool) {
 	switch failure {
 	case .Relaxed:
 		switch success {
@@ -137,7 +137,7 @@ atomic_compare_exchange_weak :: inline proc "contextless" (dst: ^$T, old, new: T
 }
 
 
-atomic_add :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) -> T {
+atomic_add :: inline proc(dst: ^$T, val: T, $order: Ordering) -> T {
 	switch order {
 	case .Relaxed:                 return intrinsics.atomic_add_relaxed(dst, val);
 	case .Release:                 return intrinsics.atomic_add_rel(dst, val);
@@ -149,7 +149,7 @@ atomic_add :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) ->
 	return T{};
 }
 
-atomic_sub :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) -> T {
+atomic_sub :: inline proc(dst: ^$T, val: T, $order: Ordering) -> T {
 	switch order {
 	case .Relaxed:                 return intrinsics.atomic_sub_relaxed(dst, val);
 	case .Release:                 return intrinsics.atomic_sub_rel(dst, val);
@@ -161,7 +161,7 @@ atomic_sub :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) ->
 	return T{};
 }
 
-atomic_and :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) -> T {
+atomic_and :: inline proc(dst: ^$T, val: T, $order: Ordering) -> T {
 	switch order {
 	case .Relaxed:                 return intrinsics.atomic_and_relaxed(dst, val);
 	case .Release:                 return intrinsics.atomic_and_rel(dst, val);
@@ -173,7 +173,7 @@ atomic_and :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) ->
 	return T{};
 }
 
-atomic_nand :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) -> T {
+atomic_nand :: inline proc(dst: ^$T, val: T, $order: Ordering) -> T {
 	switch order {
 	case .Relaxed:                 return intrinsics.atomic_nand_relaxed(dst, val);
 	case .Release:                 return intrinsics.atomic_nand_rel(dst, val);
@@ -185,7 +185,7 @@ atomic_nand :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) ->
 	return T{};
 }
 
-atomic_or :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) -> T {
+atomic_or :: inline proc(dst: ^$T, val: T, $order: Ordering) -> T {
 	switch order {
 	case .Relaxed:                 return intrinsics.atomic_or_relaxed(dst, val);
 	case .Release:                 return intrinsics.atomic_or_rel(dst, val);
@@ -197,7 +197,7 @@ atomic_or :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) -> T
 	return T{};
 }
 
-atomic_xor :: inline proc "contextless" (dst: ^$T, val: T, $order: Ordering) -> T {
+atomic_xor :: inline proc(dst: ^$T, val: T, $order: Ordering) -> T {
 	switch order {
 	case .Relaxed:                 return intrinsics.atomic_xor_relaxed(dst, val);
 	case .Release:                 return intrinsics.atomic_xor_rel(dst, val);
diff --git a/core/thread/thread_windows.odin b/core/thread/thread_windows.odin
index a558e1b0a..430997441 100644
--- a/core/thread/thread_windows.odin
+++ b/core/thread/thread_windows.odin
@@ -28,7 +28,7 @@ create :: proc(procedure: Thread_Proc, priority := Thread_Priority.Normal) -> ^T
 	win32_thread_id: u32;
 
 	__windows_thread_entry_proc :: proc "c" (t: ^Thread) -> i32 {
-		c := context;
+		c := runtime.default_context();
 		if t.use_init_context {
 			c = t.init_context;
 		}
diff --git a/examples/demo/demo.odin b/examples/demo/demo.odin
index 4ef9b2a8c..4f425b698 100644
--- a/examples/demo/demo.odin
+++ b/examples/demo/demo.odin
@@ -6,6 +6,7 @@ import "core:os"
 import "core:thread"
 import "core:time"
 import "core:reflect"
+import "core:runtime"
 import "intrinsics"
 
 
@@ -1931,6 +1932,16 @@ union_maybe :: proc() {
 	fmt.println(z, z_ok);
 }
 
+dummy_procedure :: proc() {
+	fmt.println("dummy_procedure");
+}
+
+explicit_context_definition :: proc "c" () {
+	// Try commenting the following statement out below
+	context = runtime.default_context(); 
+	dummy_procedure();
+}
+
 main :: proc() {
 	when true {
 		the_basics();
@@ -1961,5 +1972,6 @@ main :: proc() {
 		soa_struct_layout();
 		constant_literal_expressions();
 		union_maybe();
+		explicit_context_definition();
 	}
 }
diff --git a/src/check_expr.cpp b/src/check_expr.cpp
index 4d3268f44..e6812b81d 100644
--- a/src/check_expr.cpp
+++ b/src/check_expr.cpp
@@ -7411,6 +7411,12 @@ ExprKind check_call_expr(CheckerContext *c, Operand *operand, Ast *call, Type *t
 
 	Type *pt = base_type(proc_type);
 
+	if (pt->kind == Type_Proc && pt->Proc.calling_convention == ProcCC_Odin) {
+		if ((c->scope->flags & ScopeFlag_ContextDefined) == 0) {
+			error(call, "'context' has not been defined within this scope, but is required for this procedure call");
+		}
+	}
+
 	#if 0
 	if (pt->kind == Type_Proc && pt->Proc.calling_convention == ProcCC_Odin) {
 		init_core_context(c->checker);
diff --git a/src/check_type.cpp b/src/check_type.cpp
index 8d8bae1a7..8aa24a752 100644
--- a/src/check_type.cpp
+++ b/src/check_type.cpp
@@ -2512,6 +2512,8 @@ bool check_procedure_type(CheckerContext *ctx, Type *type, Ast *proc_type_node,
 	GB_ASSERT(cc > 0);
 	if (cc == ProcCC_Odin) {
 		c->scope->flags |= ScopeFlag_ContextDefined;
+	} else {
+		c->scope->flags &= ~ScopeFlag_ContextDefined;
 	}
 
 	bool variadic = false;
diff --git a/src/checker.cpp b/src/checker.cpp
index 2bf79134d..bb54fd903 100644
--- a/src/checker.cpp
+++ b/src/checker.cpp
@@ -281,6 +281,7 @@ Scope *create_scope_from_package(CheckerContext *c, AstPackage *pkg) {
 	if (s->flags & (ScopeFlag_Init|ScopeFlag_Global)) {
 		s->flags |= ScopeFlag_HasBeenImported;
 	}
+	s->flags |= ScopeFlag_ContextDefined;
 
 	return s;
 }